The present invention relates to a safety valve. More particularly, it relates to a spring loaded safety valve, particularly for hot water and/or saturated vapor.
In hot water systems the medium in normal operational conditions exists in liquid form until it reaches a valve seat. During the operation of the safety valve, hot water first exits from the safety valve, and a vapor cushion generates in a boiler because of the lowering of the liquid level. A vapor/water mixture thereby exits from the safety valve in the second opening phase. In unfavorable cases pure saturated vapor can also generate.
For safety reasons, the safety valve must be designed for the most unfavorable case. For this reason, the free cross section of the safety valve for the saturated vapor medium must provide for a considerably greater space than for hot water. Thereby, the valve cross section in the region of hot water outlet is many times greater, so that here during opening of the safety valve a pressure breakdown immediately takes place, whereby the valve obtains an impulse for closing before it has been completely opened. After closing of the safety valve, the pressure builds in striking manner again and the valve again immediately opens. Three openings and closings in fractions of seconds cause vibrations of the valve spring, whereby the safety valve begins to flutter. The frequency of 100 hertz and more can be reached. The above-mentioned valve flutter can result in damages to the system.